Process for Producing an Object Having at Least Two Moving Parts

ABSTRACT

A process for producing an object having at least two component parts ( 3, 4 ) which can move relative to one another is proposed. This involves preparing geometrical data of the entire object for a rapid prototyping process, with a predetermined minimum spacing between the moving parts being taken into consideration. According to the predetermined geometrical data, a first material as support material and a second material as material for the component parts are applied in layers, the support material filling gaps including those constituting the minimum spacing between the respective material for the component parts. Following completion of the layered construction, the support material is removed.

The invention relates to a method for manufacturing an object with at least two components which are movable relative to one another.

Rapid prototyping technology is known for manufacturing prototypes or models or other components, which may also be designed in a complex manner, and by way of this technology these objects may be manufactured according to STL (standard transformation language) data, set up previously in a CAD-program. One application possibility falling under rapid prototyping technology is the multi-jet modelling method. This method is a generative manufacturing method and permits the manufacture of patterns, prototypes or subjects from shapeless material without the application of special tools.

The deposition of the material is carried out with the help of a print head via a multitude of individual nozzles. In this manner, high-quality models for e.g. primal shapes which are true to detail, may be prepared in a cost-effective manner and within the shortest of times for subsequent processes, such as vacuum casting for example.

Thereby, the model is constructed on a component platform. Basically, the model is manufactured in a layered manner on the basis of the contour data computed for each construction plane from the STL data set. Firstly, a special support geometry is plotted for the unambiguous setting of the construction layers to be manufactured on the construction platform. The component material is subsequently deposited in the width of the print head, wherein the print head is guided by way of a computer-controlled travel mechanism. Thereafter, the construction platform is displaced by a print head width, when the model is larger than the width of the print head. The support material with regard to the layered construction is set such that overhanging structures of the component material which are provided in the layers deposited later, are supported by the layers of the support material which lie thereunder. After construction of the whole layer, the construction platform is lowered by a layer thickness, and the print heads follow this. The component material is thermoplastic and is melted and deposited through the nozzles of the print head in the form of droplets, and subsequently cured by UV-light. The additionally deposited support structure is melted away in a furnace after the printing.

As already stated, a wax-like thermoplastic is applied as a component material, for example an acrylic photopolymer, which holds together wax constituents in an acrylate base structure. The wax constituents have a melting point of approx. 65° C., and in combination with the acrylate, the models may however be subjected to a temperature of approx. 80° C. The material for the support geometry is likewise a wax, and is melted away in the heat furnace at approx. 70° C.

The advantages of the described method, when compared to other rapid prototyping systems, particularly lie in the high resolution of the models. Layer thicknesses of 800 DPI (corresponds to approx. 32 μm) may be achieved in the z-direction, and layers with a resolution of 656 DPI may be printed in the x- and y-direction. Until now, the method has been used to produce components, wherein each component was manufactured individually according to the above method and then assembled for multi-part objects. With a gear, e.g. each cog had to be printed, melted-off and placed on the shaft individually. Since the gear was assembled together at a later point in time, it was also necessary to use suitable geometries for this. E.g. with the construction of a shaft with the CAD-program, one had to provide open geometries in order to subsequently be able to assembled the cogs.

It is therefore the object of the invention to provide an object with several moving parts according to the rapid prototyping method, with which the object as a whole may be manufactured with less effort with regard to time, and with simplified geometries.

According to the invention, this object is achieved by the features of the main claim.

It is possible to manufacture the object with all parts in a direct manner, by way of the fact that geometry data is set up from the whole object with its moving, and, as the case may be, stationary components, for a rapid prototyping method, whereon a predefined minimal distance between the moving parts is taken into account, and that, in a layered manner according to the defined geometry data, a first material is deposited as a support material, and a second material as a component material, wherein the support material fills gaps including those with the minimal distance and that the support material is removed after completion of the layered construction. Thus, the additional assembly and the time effort which this entails are done away with. Moreover, one does not need to take any geometry into account or to provide this, which would permit the disassembly or assembly of the object at a later point in time. A greater stability is simultaneously achieved.

Advantageous further formations and improvements are possible by way of the features provided in the dependent claims.

The minimal distance between the moving components is dependent on the characteristics of the support material, on the size of the moving parts and/or on the possibilities of deposition. Whilst taking into account the characteristics of the support material, it is envisaged for this to be able to be led away with its removal from the region between the components. The minimal distance is a molecular layer, given a relatively low viscosity and a high resolution on depositing the support material. Advantageously, a minimal distance of greater than 0.1 mm is provided, depending on the characteristics of the support material, in particular with support wax, and on the size of the components movable to one another.

The support material is separated on account of its physical and/or chemical characteristics, which are different to the component material.

For structures which may be moved to one another, and which likewise are manufactured by way of a component material in the density range of approx. 1.01 g/cm³ (at 25° C.) and in the viscosity range of 12 to 14 mPa·s (at 80° C.), it is likewise necessary on account of the resolution, to maintain a distance of at least 100 to 130 μm between the individual components, in order to ensure the mobility. For this, the surfaces lying parallel to one another and which are to be movable to one another, should not be greater than 30 mm². If this is indeed the case, then the viscosity of the support material is an additional determining factor, since this is prevented from flowing away by the acting capillary forces. For this reason, a distance of two surfaces lying parallel opposite one another of at least 0.3 mm is necessary for a support material of the viscosity range of about 10 to 12 mPa·s (at 80° C.) and of the density range of approx. 0.91 g/cm³.

If material must flow away through a hole, i.e. from the inside of a cavity to the outside, then the diameter of this opening on account of the viscosity (region: viscosity region of about 10 to 12 mPa·s at 80° C.) of the support material must be at least 1 mm.

It is particularly advantageous for the support material to be selected such that it has a lower melting point that the component material, by which means the support material may be led away in a simple manner by way of increasing the temperature beyond the melting point. Other support materials are also conceivable, which may be separated from the component material by way of etching, plasma treatments, different solubilities in reagents, or subjection to a radiation. The component material layers and support material layers may be deposited in a different manner, e.g. by way of printing, by way of dispersing, by way of screen printing and likewise. Advantageously, the different layers of component material and support material are deposited through a printing head via nozzles, which is controlled depending on the geometry data. The method for the construction of the object by way of printing head thus permits a simple manufacture.

In an advantageous embodiment example, additional geometrical measures are taken on, in or between the components, such as channels, grooves or holes, which simplify a release and/or flowing-away of the support material.

For example, it is now possible to manufacture an object with a component, which has a structure enclosing a cavity, e.g. a ball, wherein a further component, e.g. a further ball is received in this structure, e.g. the first mentioned ball in a moving manner. With a manufacturing process of two different balls which takes its course in a separate manner, it is no longer possible to integrate these afterwards. An assembly is superfluous with the help of the method according to the invention. It is merely necessary to provide one or more smaller holes in the outer ball, in order with this, to permit the draining of the support material, e.g. of the support wax. Here too, the diameter is dependent on the characteristics of the support material, and with support wax a diameter of 1 mm is already adequate for these holes.

It is now possible to manufacture more complex objects which have moving parts, with a print procedure. By way of this, it is further possible to manufacture components which may be applied beyond the stage of an illustrational pattern, also as functional prototypes. For example, these prototypes may be used directly in mechanical, electronic or mechatronic assemblies of a machine. This has hitherto only been possible to a limited extent, since the characteristics of the component manufactured of wax only permit this to be used in a very limited field of application. Future or other materials may expand this restricted field of application. These may for example be eclectically and/or thermally conductive plastics (e.g. by way of metallic fillers) or other types of plastics or metals, which for example have an improved modulus of elasticity, and improved bending modulus, an increased bending strength, a lower extension at break, a greater tensile strength and/or an increased application temperature.

An object with moving parts is represented in the drawing and its method for manufacturing is explained in more detail in the following description. There are shown in

FIG. 1: a plan view of a gear,

FIG. 2: a perspective view in a taken-apart condition of the gear, according to FIG. 1,

FIG. 3: a perspective view of the gear according to FIG. 1 and

FIG. 4: a view of the gear according to FIG. 1 seen from below.

The gear which is to be manufactured with the method according to the invention, and is represented in the FIGS. 1, 3 and 4, comprises a membered-like base plate 1, on which stationary shafts 2 for cogs 3 connected to it are provided.

The cogs 3 and shafts 2 are shown separately from one another in FIG. 2 for a better understanding, although they are manufactured in the assembled condition. Furthermore, a smaller drive cog 4 is provided, which comprises a shaft stub 5 which is firmly connected to it, which engages through a recess 6 in the base plate 1 and which may be connected to an electric motor which is not represented.

A distance or play is provided between the cogs 3, 4 and the shafts 2, as well as between the shaft stub 5 and the recess 6.

The cogs 3 are held on the shafts 2 by way of a bar 7, whereas the drive cog 4 is fixed in the recess by way of a flange 8.

A distance between the cog 3 and the base plate 1 is specified at 9, with is to be kept to during manufacture, so that the support wax which is used with this, may flow away. Such a distance is always provided if two moving parts lie opposite one another, as is the case with the distance mentioned above, between the cogs 3 and shafts or the cog 4 with the shaft stub 5 and the base plate and recess 6, or flange 8 and the base plate 1. Additionally, holes 10 as geometries supporting the flowing-away of the support wax are incorporated in the base plate 1 around the recess 6, as well as also in the drive cog 4.

The cogs 3 have a diameter of approx. 3 cm and the drive cog 4 a diameter of approx. 1 cm in the embodiment example. In such a case, the distance 9 and the respective distances mentioned above are to be dimensioned to at least 0.1 to 0.13 mm. This distance increases to at least 0.3 mm if the surfaces lying parallel opposite to one another are larger than 30 mm², i.e. if support wax of an area of greater than 30 mm² must be melted away. The holes 10 must have a diameter of at least 1 mm, in order to permit the support wax to flow away.

The components of the gear have firstly been drawn individually in a design program, and subsequently assembled with this program into an assembly. On assembly with the design program, care was taken that the mentioned minimal distances of the parts to one another were adhered to, so that the support wax may correctly flow away during the melting procedure in the heating furnace. The CAD-drawing is a digital plane picture of the later gear which is represented in the FIGS. 1 to 4, and is present as an STL-file.

As has been specified above, a base structure of support material, such as support wax, is deposited on a construction platform, whereupon the various layers are deposited with a printer to which the STL-file is supplied, in the different materials, the component material and the support material. The construction platform and the printer thereby may be displaced relative to one another in a three-dimensional manner.

Gaps or distances as previously computed, are provided between the respective component regions of each layer, and these are filled out with the support material, wherein the different materials are deposited in a geometrically correct manner with the printing procedure of the layer. After the finished construction in the 3D-printer, which encompasses the gear with the support material lying therebetween, this support material, as the case may be, is cured, and subsequently melted away in an furnace. A gear with moving cogs remains after the melting away. 

1. A method for manufacturing an object with at least two components which are movable relative to one another, wherein geometry data is set up from the whole object for a rapid prototyping method, wherein a predefined minimal distance between the moving components is taken into account, wherein a first material as a support material and a second material as a component material are deposited in a layered manner according to the predefined geometry data, wherein the support material fills out gaps including those with the minimal distance between the respective component material, and wherein the support material is removed after the completion of the layered construction.
 2. A method according to claim 1, wherein the minimal distance between the components is determined such that while taking account of the characteristics of the support material, this may be led away between the components, on its removal out of the respective region.
 3. A method according to claim 1 wherein at least one molecular layer of the support material is provided as a minimal distance, depending in the characteristics of the support material
 4. A method according to claim 1 wherein a minimal distance between the moving parts of larger than 0.1 mm is provided.
 5. A method according to claim 1 wherein the support material is selected such that it may be separated on account of at least one of its physical and chemical properties which are different with respect to the component material.
 6. A method according to claim 1 wherein the support material has a lower melting point than the component material, and wherein the support material is led away by way of increasing the temperature beyond its melting point.
 7. A method according to claim 1 wherein the support material is wax which has a melting point in the range of 60 to 70°.
 8. A method according to claim 1 wherein the component material and the support material are deposited by way of one of printing, dispensing, and screen printing.
 9. A method according to claim 1 wherein the component material and support material are deposited in a layered manner onto a platform by way of at least one application apparatus which is controlled depending on the geometry data, and are subsequently cured.
 10. A method according to claim 1 wherein additional geometric measures are made at at least one of on the components, in the components, and between the components, which simplify at least one of a release and flowing away of the support material.
 11. A method according to claim 10, wherein the additional geometric measures are openings, channels or grooves.
 12. A method according to claim 11, wherein the opening is dimensioned such that it has a diameter of at least 1 mm.
 13. A method according to claim 1 wherein a structure enclosing a cavity is selected as one of the at least two movable components, and a component accommodated in the cavity in a movable manner is selected as the other component, wherein at least one opening is provided in the outer structure for the flowing away of the support material.
 14. A method according to claim 1 for manufacturing a gear with at least two cogs.
 15. A gear manufactured according to claim 1 wherein the components are cogs and shafts. 